Positive company updates and a more positive mood about the current crises in Ukraine and Gaza have helped support the market in early trading.

But Tesco has slumped to a near 10 year low, down 2.35p at 275p on continuing concerns about a possible price war with J Sainsbury, 1.3p lower at 312.5p, and Morrisons, up 0.2p at 171.7p, following the proposed departure of chief executive Philip Clarke.

Among the gainers BHP Billiton is 13.5p better at £20.68 after the mining group beat full year guidance for iron ore production by 4%. The company's chief executive Andrew Mackenzie said:

We expect to maintain strong momentum and remain on track to generate group production growth of 16% over the two years to the end of the 2015 financial year.

The news has lifted rival Rio Tinto by 8p to £33.45 and Anglo American by 4p to 1604.5p.

Elsewhere outsourcing group Capita has climbed 43p to £11.98 after it reported a 16% rise in underlying half year profit to £238m.

But SSE is leading the fallers, down 49p at £14.92 after the energy group's shares went ex-dividend. London Stock Exchange slipped 11p to £19.35 for the same reason.

The group reports first half numbers on 6 August. Following the pre-close update where management lowered expectations, we are not expecting surprises in the headline numbers; instead our focus will be on the detail in terms of capital and asset quality. We have lowered our estimates [2014/15/16 estimates cut by 12%/5%/3% respectively] to reflect the weaker guidance given, and our target price declines to 1,150p (from 1,200p).

Overall the FTSE 100 has edged up 8.20 points to 6803.54, unmoved by Bank of England minutes which showed a 9-0 vote for keeping rates and quantitative easing unchanged.

Among the mid-caps Renishaw has soared 15% to £16.93 as the engineering group said a strong fourth quarter had helped it lift full year profits by 17%. The company won large orders from an Asian customer and also sold its stake in software group Delcam. Analyst Michael Blogg at Investec said:

Renishaw retains a huge capacity to surprise and has done so on the upside today. Full year revenue exceeded our estimate by £13.5m (almost all in the Metrology division and mainly in the Far East) and this dropped through to earnings. There was 8% underlying growth, excluding lumpy unpredictable orders in both years. This good news is likely to be reflected in the share price after a period of underperformance. Our estimates and target price are placed under review, but we are comfortable with a buy recommendation.